A couple of years back, I was on a LGW to VCE flight on BA. Safety briefing starts, about half the PAX carried on talking and not paying attention. Purser stops the briefing and gets on the PA and tells the PAX in no uncertain terms that this briefing is for their safety and and it also affects her, so they BETTER listen! When she stops, a few PAX clap, with cries of 'hear, hear'. Re runs safety briefing in silence, and gets attention - and a number of PAX later congratulating her on her stand.
She did seem to preene herself a bit with getting some PAX support - I suspect it doesn't always happen.
I'm surprised nobody else appears to check that there REALLY is a lifejacket under the seat and it's not been nicked. I have on one occasion found on BA that it wasn't there, and it took about 20 seconds after telling the CC and them checking, for another one to appear. And we hadn't even pushed back!